1066 - William of Normandy invaded and conquered England. This why so many English words are from French.
1492 - Columbus "discovered" America. Schoolchildren learn a rhyme:
"In fourteen hundred and ninety-two,
Columbus sailed the ocean blue."
1776 - US declares independence from Britain, This is what Americans celebrate every year on July 4th, their national day.
1861-1865 - The American Civil War, or "War between the States," North against South.
1914-1918 - The First World War. The US entered in 1917.
1939-1945 - The Second World War. The US entered in 1941.